Pattern forming material and pattern forming method

ABSTRACT

The pattern forming material of the present invention includes a polymer having a group which generates an acid when the polymer is irradiated with an energy beam or heated and a compound which generates a base when the compound is irradiated with an energy beam. The polymer is a binary polymer or a polymer of a higher degree obtained by polymerizing another group with a compound represented by the following general formula:where R1 indicates a hydrogen atom or an alkyl group, and R2 and R3 independently indicate a hydrogen atom, an alkyl group, a phenyl group or an alkenyl group, or together indicate a cyclic alkyl group, a cyclic alkenyl group, a cyclic alkyl group having a phenyl group or a cyclic alkenyl group having a phenyl group.

This application is a divisional of application Ser. No. 09/026,483filed Feb. 19, 1998 now U.S. Pat. No. 6,017,683.

BACKGROUND OF THE INVENTION

The present invention relates to a method for forming a fine resistpattern in a process for fabricating a semiconductor integrated circuit(IC) device and the like (in this specification, such a method will besimply referred to as a “pattern forming method”), and also relates to amaterial for forming such a pattern used in the method (in a similarmanner, such a material will be simply referred to as a “pattern formingmaterial” in this specification).

Conventionally, in fabricating ICs, large-scale integrated circuits(LSIs) and the like, a pattern has been formed by a photolithographyprocess using UV light. However, a light source utilizing a shorterwavelength has been used more and more frequently as the size of asemiconductor device has become increasingly small. Recently, in thecase of using a light source utilizing a shorter wavelength, a surfaceimaging process using a dry development technique has been developed inorder to increase the focal depth and to improve a practical resolution.

The surface imaging process is disclosed, for example, in U.S. Pat. No.5,278,029. The patent discloses a negative type surface modificationprocess. Specifically, according to the disclosed process, first, apolysiloxane film is selectively formed on the surface of a resist film,which is made of a resist material generating an acid when the materialis exposed to light. Thereafter, the resist film is dry-etched by usingthe polysiloxane film as a mask, thereby forming a resist pattern.

Hereinafter, a conventional method for forming the resist pattern willbe described with reference to FIGS. 9(a) through 9(d).

In the exemplary method to be described below, a copolymer of1,2,3,4-tetrahydronaphthylideneimino-p-styrene sulfonate (NISS) andmethyl methacrylate (MMA) is assumed to be used as a resist materialgenerating an acid when the material is exposed to light.

First, as shown in FIG. 9(a), when a resist film 11, which is applied ona semiconductor substrate 10 and is made of a material generating anacid through the exposure to light, is irradiated with ArF excimer laserbeam 14 by using a mask 13, an acid is generated in an exposed area 11 aof the resist film 11. The generated acid contributes to turning theexposed area 11 a into a hydrophilic area. As a result, water in the aircan be easily adsorbed into the exposed area 11 a. Consequently, a thinwater-adsorbing layer 15 is formed in the vicinity of the surface of theexposed area 11 a as shown in FIG. 9(b).

Next, when an alkoxysilane gas 16 is introduced onto the surface of theresist film 11, the acid, which has been generated on the surface of theexposed area 11 a, works as a catalyst, thereby hydrolyzing anddehydrating alkoxysilane. As a result, a metal oxide film 17 is formedon the surface of the exposed area 11 a, as shown in FIG. 9(c).Subsequently, when the resist film 11 is dry-etched in accordance with areactive ion etching (RIE) technique using O₂ plasma 18 while using themetal oxide film 17 as a mask, a fine resist pattern 19 is formed asshown in FIG. 9(d).

In this pattern forming method, a resist pattern is formed by performingthe steps of: generating an acid in an exposed area of a resist film;selectively forming a metal oxide film in the exposed area by using thegenerated acid as a catalyst; and dry-etching the resist film by usingthe metal oxide film as a mask. Thus, this method is a negative typelithography process in which a resist pattern is formed in the exposedarea of a resist film.

The negative type lithography process has the following problems in, forexample, forming contact holes for connecting multi-layerinterconnections of an integrated circuit.

First, the usage itself of a mask, generally employed in an exposureprocess step, causes the following problems. In the lithography processfor forming contact holes, the opening ratio of the mask becomes veryhigh if the negative type lithography process is used as describedabove. Specifically, a light blocking film against the exposingradiation is formed only in the portions corresponding to the contactholes on the mask. On the other hand, the light blocking film is removedand quartz of the mask substrate is exposed in the portions other thanthe contact hole portions, because the former portions can transmit theexposing radiation. In general, the ratio of the area occupied by all ofthe contact holes to the entire area of a semiconductor chip is verysmall. Thus, the opening ratio of the mask, i.e., the ratio of the areaoccupied by the exposed quartz to the area of the light blocking film onthe mask becomes very high.

When the opening ratio of the mask becomes high, the process is muchmore likely to be affected by the contamination with ambient dust. Morespecifically, even when dust is adhered to the light blocking filmportions of the mask, the dust hardly affects the process. However, ifthe dust is adhered to the transmissible portions of the mask, thenthese portions are turned into light blocking portions. When theexposure is performed by using such a mask to which dust has beenadhered, pattern defects are caused in the portions to which the dusthas been adhered and the portions corresponding thereto. As can beunderstood from the foregoing description, since the opening ratio ofthe mask becomes high in the negative type lithography process, theprocess is more likely to be affected by dust. As a result, this processhas a problem in that the resulting yield is likely to decrease.

Next, a second problem will be described. In the lithography process forforming contact holes, a half-tone type mask is sometimes used in orderto attempt to increase the focal depth. However, in most cases, theeffect of increasing the focal depth can be attained only in a positivetype lithography process and cannot be attained in the negative typelithography process. Thus, in forming contact holes, the focal depthbecomes adversely small in the negative type process as compared withthe positive type process.

The first and second problems described above are caused not only whenthe contact holes are formed, but also when a mask having a large lighttransmissible area is used and when the increase in focal depth isattempted.

SUMMARY OF THE INVENTION

In view of the above-mentioned conventional problems, the presentinvention has been devised for the purpose of realizing a positive typesurface modification process substitutable for the negative type surfacemodification process.

In order to accomplish this object, according to the present invention,a resist film is made of a polymer including a group which generates anacid when the polymer is heated or irradiated with a first energy beamand a compound which generates a base when the compound is irradiatedwith a second energy beam having an energy band different from that ofthe first energy beam. In the exposed area of the resist film, the acidwhich has been generated from the polymer is neutralized with the basewhich has been generated from the compound. On the other hand, in theunexposed area of the resist film, the acid which has been generatedfrom the polymer is left and a metal alkoxide is reacted by the catalystfunction of the residual acid, thereby forming a metal oxide film.

The first pattern forming material of the present invention includes apolymer including a group which generates an acid when the polymer isheated and a compound which generates a base when the compound isirradiated with an energy beam.

When the resist film, made of the first pattern forming material, isheated, an acid is generated from the polymer over the entire surface ofthe film. Thereafter, when the resist film is exposed to the energybeam, a base is generated from the compound and the acid which has beengenerated from the polymer is neutralized with the base which has beengenerated from the compound in the exposed area of the resist film. Onthe other hand, in the unexposed area of the resist film, the acid isleft. Thus, since the acid can be selectively left only in the unexposedarea of the resist film, a positive type surface modification process isrealized.

The second pattern forming material of the present invention includes apolymer including a group which generates an acid when the polymer isirradiated with a first energy beam having a first energy band and acompound which generates a base when the compound is irradiated with asecond energy beam having a second energy band which is different fromthe first energy band.

When the entire surface of the resist film, made of the second patternforming material, is exposed to the first energy beam, an acid isgenerated from the polymer over the entire surface of the film. When theresist film is exposed to the second energy beam, a base is generatedfrom the compound and the acid which has been generated from the polymeris neutralized with the base which has been generated from the compoundin the area of the resist film which has been exposed to the secondenergy beam. On the other hand, in the area of the resist film which hasnot been exposed to the second energy beam, the acid is left. Thus,since the acid can be selectively left only in the area of the resistfilm which has not been exposed to the second energy beam, a positivetype surface modification process is realized.

Moreover, since the first or the second pattern forming material is amixture of a polymer including a group which generates an acid and acompound which generates a base, the polymer and the compound can bemixed at a more flexible ratio.

In the first or the second pattern forming material, the polymer ispreferably a binary polymer or a polymer of a higher degree obtained bypolymerizing another group with a compound represented by the followinggeneral formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group. In this case, the ratio of thecompound represented by Chemical Formula 1 to the binary polymer or thepolymer of a higher degree may be set at an arbitrary value. However, inorder to facilitate the neutralization with the base, the ratio ispreferably equal to or lower than about 50 mol %.

Furthermore, in the first pattern forming material, the polymer ispreferably a binary polymer or a polymer of a higher degree obtained bypolymerizing another group with a compound represented by the followinggeneral formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₄ indicatesan alkyl group, an alkenyl group, a cyclic alkyl group or a cyclicalkenyl group.

The compound represented by this general formula (Chemical Formula 2) ischaracterized by hardly generating an acid even when the compound isirradiated with light (or energy beam). In this case, the ratio of thecompound represented by Chemical Formula 2 to the binary polymer or thepolymer of a higher degree may be set at an arbitrary value. However, inorder to facilitate the neutralization with the base, the ratio ispreferably equal to or lower than about 50 mol %.

If the polymer is a binary polymer or a polymer of a higher degreeobtained by polymerizing another group with the compound represented bythe former general formula (Chemical Formula 1) in the first or thesecond pattern forming material, or if the polymer is a binary polymeror a polymer of a higher degree obtained by polymerizing another groupwith the compound represented by the latter general formula (ChemicalFormula 2) in the first pattern forming material, then sulfonic acid,generated from the polymer, functions as a strong catalyst when a metaloxide film is formed in the unexposed area of the resist film. As aresult, a positive type surface modification process is realized at ahigh contrast.

Moreover, in the first or the second pattern forming material, thecompound is preferably acyloxime, a benzyloxycarbonyl compound orformamide.

In such a case, amine is generated in the exposed area of the resistfilm, and is strongly neutralized with the acid. As a result, a positivetype surface modification process is realized at a high contrast.

The first pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer having a group whichgenerates an acid when the polymer is heated and a compound whichgenerates a base when the compound is irradiated with an energy beam; asecond step of generating the acid from the polymer by heating theresist film; a third step of irradiating the resist film with the energybeam through a mask having a desired pattern shape, generating the basefrom the compound in an exposed area of the resist film and therebyneutralizing the acid which has been generated from the polymer with thebase which has been generated from the compound in the exposed area ofthe resist film; a fourth step of supplying a metal alkoxide onto theresist film and thereby forming a metal oxide film on a surface of anunexposed area of the resist film; and a fifth step of forming a resistpattern of the resist film by dry-etching the resist film by using themetal oxide film as a mask.

In accordance with the first pattern forming method of the presentinvention, when the resist film is heated, an acid is generated from thepolymer over the entire surface of the resist film. Thereafter, when theresist film is exposed to the energy beam, a base is generated from thecompound and the acid which has been generated from the polymer isneutralized with the base which has been generated from the compound inthe exposed area of the resist film. On the other hand, in the unexposedarea of the resist film, the acid is left. Next, when a metal alkoxideis supplied to the resist film, the metal alkoxlde is reacted with theresidual acid functioning as a catalyst to form a metal oxide film inthe unexposed area of the resist film. On the other hand, since theexposed area of the resist film has been neutralized, no metal oxidefilm is formed therein. That is to say, the metal oxide film is formedonly in the unexposed area of the resist film thanks to the catalyticfunction of the acid. Thus, by performing a dry etching process by usingthe metal oxide film as a mask, a fine resist pattern having a desiredpositive type pattern shape can be formed.

In the first pattern forming method, the fourth step preferably includesa step of causing the unexposed area of the resist film to absorb water.

In such a case, water diffuses from the surface of the resist film intoa deep level in the unexposed area of the resist film. As a result, thethickness of the metal oxide film to be formed on the surface of theunexposed area of the resist film becomes large.

The second pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer having a group whichgenerates an acid when the polymer is heated, and a compound whichgenerates a base when the compound is irradiated with an energy beam; asecond step of generating the base from the compound in an exposed areaof the resist film by irradiating the resist film with the energy beamthrough a mask having a desired pattern shape; a third step of heatingthe resist film, generating the acid from the polymer and therebyneutralizing the base which has been generated from the compound withthe acid which has been generated from the polymer in the exposed areaof the resist film; a fourth step of supplying a metal alkoxide onto theresist film and forming a metal oxide film on a surface of an unexposedarea of the resist film; and a fifth step of forming a resist pattern ofthe resist film by dry-etching the resist film by using the metal oxidefilm as a mask.

In accordance with the second pattern forming method of the presentinvention, when the resist film is exposed to the energy beam, a base isgenerated from the compound in the exposed area of the resist film.Thereafter, when the resist film is heated, an acid is generated fromthe polymer over the entire surface of the resist film. In the exposedarea of the resist film, the base which has been generated from thecompound is neutralized with the acid which has been generated from thepolymer. On the other hand, in the unexposed area of the resist film,the acid is left. Next, when a metal alkoxide is supplied to the resistfilm, the metal alkoxide is reacted with the residual acid functioningas a catalyst to form a metal oxide film in the unexposed area of theresist film. On the other hand, since the exposed area of the resistfilm has been neutralized, no metal oxide film is formed therein. Thatis to say, the metal oxide film is formed only in the unexposed area ofthe resist film thanks to the catalytic function of the acid. Thus, byperforming a dry etching process by using the metal oxide film as amask, a fine resist pattern having a desired positive type pattern shapecan be formed.

In the first or the second pattern forming method, the fourth steppreferably includes a step of causing the unexposed area of the resistfilm to absorb water.

In such a case, water diffuses from the surface of the resist film intoa deep level in the unexposed area of the resist film. As a result, thethickness of the metal oxide film to be formed on the surface of theunexposed area of the resist film becomes large.

The third pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a compound which generates abase when the compound is irradiated with a first energy beam having afirst energy band and a polymer which generates an acid when the polymeris irradiated with a second energy beam having a second energy bandwhich is different from the first energy band; a second step ofgenerating the base from the compound in an area of the resist filmwhich has been exposed to the first energy beam by irradiating theresist film with the first energy beam through a mask having a desiredpattern shape; a third step of irradiating an entire surface of theresist film with the second energy beam, generating the acid from thepolymer over the entire surface of the resist film and therebyneutralizing the base which has been generated from the compound withthe acid which has been generated from the polymer in the area of theresist film which has been exposed to the first energy beam; a fourthstep of supplying a metal alkoxide onto the resist film and therebyforming a metal oxide film on a surface of an area of the resist filmwhich has not been exposed to the first energy beam; and a fifth step offorming a resist pattern of the resist film by dry-etching the resistfilm by using the metal oxide film as a mask.

In accordance with the third pattern forming method of the presentinvention, when the resist film is exposed to the first energy beam, abase is generated from the compound in the area of the resist film whichhas been exposed to the first energy beam. Thereafter, when the entiresurface of the resist film is exposed to the second energy beam, an acidis generated from the polymer. In the area of the resist film which hasbeen exposed to the first energy beam, the base which has been generatedfrom the compound is neutralized with the acid which has been generatedfrom the polymer. On the other hand, in the area of the resist filmwhich has not been exposed to the first energy beam, the acid is left.Next, when a metal alkoxide is supplied to the resist film, the metalalkoxide is reacted with the residual acid functioning as a catalyst toform a metal oxide film in the area of the resist film which has notbeen exposed to the first energy beam. On the other hand, since the areaof the resist film, which has been exposed to the first energy beam, hasbeen neutralized, no metal oxide film is formed therein. That is to say,the metal oxide film is formed only in the area of the resist film whichhas not been exposed to the first energy beam thanks to the catalyticfunction of the acid. Thus, by performing a dry etching process by usingthe metal oxide film as a mask, a fine resist pattern having a desiredpositive type pattern shape can be formed.

In the third pattern forming method, the fourth step preferably includesa step of causing the area of the resist film, which has not beenexposed to the first energy beam, to absorb water.

In such a case, water diffuses from the surface of the resist film intoa deep level in the area of the resist film which has not been exposedto the first energy beam. As a result, the thickness of the metal oxidefilm to be formed on the surface of the area of the resist film, whichhas not been exposed to the first energy beam, becomes large.

The fourth pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer which generates anacid when the polymer is irradiated with a first energy beam having afirst energy band and a compound which generates a base when thecompound is irradiated with a second energy beam having a second energyband which is different from the first energy band; a second step ofgenerating the acid from the polymer in the resist film by irradiatingan entire surface of the resist film with the first energy beam; a thirdstep of irradiating the resist film with the second energy beam througha mask having a desired pattern shape, generating the base from thecompound in an area of the resist film which has been exposed to thesecond energy beam and thereby neutralizing the acid which has beengenerated from the polymer with the base which has been generated fromthe compound in the area of the resist film which has been exposed tothe second energy beam; a fourth step of supplying a metal alkoxide ontothe resist film and thereby forming a metal oxide film on a surface ofan area of the resist film which has not been exposed to the secondenergy beam; and a fifth step of forming a resist pattern of the resistfilm by dry-etching the resist film by using the metal oxide film as amask.

In accordance with the fourth pattern forming method of the presentinvention, when the entire surface of the resist film is exposed to thefirst energy beam, an acid is generated from the polymer over the entiresurface of the resist film. Thereafter, when the resist film is exposedto the second energy beam, a base is generated from the compound and theacid which has been generated from the polymer is neutralized with thebase which has been generated from the compound in the area of theresist film which has been exposed to the second energy beam. On theother hand, in the area of the resist film which has not been exposed tothe second energy beam, the acid is left. Next, when a metal alkoxide issupplied to the resist film, the metal alkoxide is reacted with theresidual acid functioning as a catalyst to form a metal oxide film inthe area of the resist film which has not been exposed to the secondenergy beam. On the other hand, since the area of the resist film whichhas been exposed to the second energy beam has been neutralized, nometal oxide film is formed therein. That is to say, the metal oxide filmis formed only in the area of the resist film which has not been exposedto the second energy beam thanks to the catalytic function of the acid.Thus, by performing a dry etching process by using the metal oxide filmas a mask, a fine resist pattern having a desired positive type patternshape can be formed.

In the fourth pattern forming method, the fourth step preferablyincludes a step of causing the area of the resist film, which has notbeen exposed to the second energy beam, to absorb water.

In such a case, water diffuses from the surface of the resist film intoa deep level in the area of the resist film which has not been exposedto the second energy beam. As a result, the thickness of the metal oxidefilm to be formed on the surface of the area of the resist film, whichhas not been exposed to the second energy beam, becomes large.

In the first to the fourth pattern forming methods, the polymer ispreferably a binary polymer or a polymer of a higher degree obtained bypolymerizing another group with the compound represented by thefollowing general formula

where R₁ indicates a hydrogen atom or an alkyl group, and R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group. In this case, the ratio of thecompound represented by this general formula (Chemical Formula 1) to thebinary polymer or the polymer of a higher degree may be set at anarbitrary value. However, in order to facilitate the neutralization withthe base, the ratio is preferably equal to or lower than about 50 mol %.

Furthermore, in the first or the second pattern forming method, thepolymer is preferably a binary polymer or a polymer of a higher degreeobtained by polymerizing another group with a compound represented bythe following general formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₄ indicatesan alkyl group, an alkenyl group, a cyclic alkyl group or a cyclicalkenyl group.

The compound represented by this general formula (Chemical Formula 2) ischaracterized by hardly generating an acid even when the compound isirradiated with light (or energy beam). In this case, the ratio of thecompound represented by this general formula (Chemical Formula 2) to thebinary polymer or the polymer of a higher degree may be set at anarbitrary value. However, in order to facilitate the neutralization withthe base, the ratio is preferably equal to or lower than about 50 mol %.

If the polymer is a binary polymer or a polymer of a higher degreeobtained by polymerizing another group with the compound represented bythe former general formula (Chemical Formula 1) in the first to thefourth pattern forming methods, or if the polymer is a binary polymer ora polymer of a higher degree obtained by polymerizing another group withthe compound represented by the latter general formula (Chemical Formula2) in the first pattern forming method, then sulfonic acid functions asa strong catalyst when a metal oxide film is formed in the unexposedarea of the resist film. As a result, a metal oxide film having a highselectivity can be formed only in the unexposed area of the resist film,and thus a more fine resist pattern having a desired positive typepattern shape can be formed.

Moreover, in the first to the fourth pattern forming methods, thecompound is preferably acyloxime, a benzyloxy-carbonyl compound orformamide. Specifically, acyloxime may beO-phenylacetyl-aceto-α-naphtone-oxime,O-phenylacetyl-aceto-β-phenone-oxime, O-phenylacetyl-acetophenone-oximeor the like.

In such a case, amine is generated in the exposed area of the resistfilm, and is strongly neutralized with the acid. As a result, a metaloxide film having a high selectivity can be formed only in the unexposedarea of the resist film, and a more fine resist pattern having a desiredpositive type pattern shape can be formed.

The fifth pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer having a group whichgenerates an acid when the polymer is heated and a compound whichgenerates a base when the compound is irradiated with an energy beam; asecond step of generating the acid from the polymer by heating theresist film; a third step of irradiating the resist film with the energybeam through a mask having a desired pattern shape so as to transfer thepattern, performing a water treatment on the resist film in a vaporphase or in a liquid phase, and thereby generating the base from thecompound in an exposed area of the resist film and neutralizing the basewhich has been generated from the compound with the acid which has beengenerated from the polymer in the exposed area of the resist film; afourth step of exposing the resist film to a water vapor environment andthen to a mixed gas environment of water vapor and a metal alkoxide andthereby forming a metal oxide film on a surface of an unexposed area ofthe resist film; and a fifth step of forming a resist pattern of theresist film by dry-etching the resist film by using the metal oxide filmas a mask.

In accordance with the fifth pattern forming method of the presentinvention, after the resist film, in which the acid has been generated,is exposed to light, a water treatment is performed on the resist filmin a vapor phase or in a liquid phase. Thus, in the exposed area of theresist film, a sufficient amount of base for neutralizing the acid ofthe resist film is generated from the compound, so that the acid is notleft. As a result, no metal oxide film is formed in the exposed area.Therefore, no residue of the metal oxide film is formed on thesemiconductor substrate after a resist pattern has been formed thereon.

The sixth pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer having a group whichgenerates an acid when the polymer is heated and a compound whichgenerates a base when the compound is irradiated with an energy beam; asecond step of generating the acid from the polymer by heating theresist film; a third step of irradiating the resist film with the energybeam through a mask having a desired pattern shape so as to transfer thepattern, retaining the resist film within an inert gas environment, andthereby generating the base from the compound in an exposed area of theresist film and neutralizing the base which has been generated from thecompound with the acid which has been generated from the polymer in theexposed area of the resist film; a fourth step of exposing the resistfilm to a water vapor environment and then to a mixed gas environment ofwater vapor and a metal alkoxide and thereby forming a metal oxide filmon a surface of an unexposed area of the resist film; and a fifth stepof forming a resist pattern of the resist film by dry-etching the resistfilm by using the metal oxide film as a mask.

In accordance with the sixth pattern forming method of the presentinvention, after the resist film, in which an acid has been generated,is exposed to light, the resist film is retained within an inert gasenvironment. Thus, in the exposed area of the resist film, a sufficientamount of base for neutralizing the acid of the resist film is generatedfrom the compound, so that the acid is not left. As a result, no metaloxide film is formed in the exposed area. Therefore, no residue of themetal oxide film is formed on the semiconductor substrate after a resistpattern has been formed thereon.

The seventh pattern forming method of the present invention includes: afirst step of forming a resist film by coating a semiconductor substratewith a pattern forming material including a polymer having a group whichgenerates an acid when the polymer is heated and a compound whichgenerates a base when the compound is irradiated with an energy beam; asecond step of generating the acid from the polymer by heating theresist film; a third step of irradiating the resist film with the energybeam through a mask having a desired pattern shape so as to transfer thepattern, exposing the resist film to a water vapor environment within aninert gas environment, and thereby generating the base from the compoundin an exposed area of the resist film and neutralizing the base whichhas been generated from the compound with the acid which has beengenerated from the polymer in the exposed area of the resist film; afourth step of exposing the resist film to a mixed gas environment ofwater vapor and a metal alkoxide and thereby forming a metal oxide filmon a surface of an unexposed area of the resist film; and a fifth stepof forming a resist pattern of the resist film by dry-etching the resistfilm by using the metal oxide film as a mask.

In accordance with the seventh pattern forming method of the presentinvention, after the resist film, in which an acid has been generated,is exposed to light, the resist film is exposed to a water vaporenvironment within an inert gas environment. Thus, in the exposed areaof the resist film, a sufficient amount of base for neutralizing theacid of the resist film is generated from the compound, and the acid isnot left. As a result, no metal oxide film is formed in the exposedarea. Therefore, no residue of the metal oxide film is formed on thesemiconductor substrate after a resist pattern has been formed thereon.

In addition, in accordance with the seventh pattern forming method,since the resist film is exposed to a water vapor environment within aninert gas environment, it is possible to omit the step of exposing theresist film to a water vapor environment, which step is to be performedbefore the step of exposing the resist film to a mixed gas environmentof water vapor and a metal alkoxide is performed.

Thus, in accordance with the fifth to the seventh pattern formingmethods of the present invention, since no residue of the metal oxidefilm is formed on the semiconductor substrate after a resist pattern hasbeen formed thereon, it is possible to eliminate the defect factorsresulting from such a residue during succeeding process steps. As aresult, the yield can be increased in a semiconductor fabricationprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) through 1(d) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the first embodiment of thepresent invention.

FIGS. 2(a) through 2(d) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the second or the thirdembodiment of the present invention.

FIGS. 3(a) through 3(c) are cross-sectional views showing the precedingprocess steps of a pattern forming method in the fourth embodiment ofthe present invention.

FIGS. 4(a) and 4(b) are cross-sectional views showing the succeedingprocess steps of the pattern forming method in the fourth embodiment ofthe present invention.

FIGS. 5(a) through 5(c) are cross-sectional views showing the precedingprocess steps of a pattern forming method in the fifth embodiment of thepresent invention.

FIGS. 6(a) through 6(c) are cross-sectional views showing the succeedingprocess steps of the pattern forming method in the fifth embodiment ofthe present invention.

FIGS. 7(a) and 7(b) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the sixth embodiment of thepresent invention.

FIGS. 8(a) and 8(b) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the seventh embodiment ofthe present invention.

FIGS. 9(a) through 9(d) are cross-sectional views showing the respectiveprocess steps of a conventional pattern forming method.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

FIGS. 1(a) through 1(d) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the first embodiment of thepresent invention.

As a resist material, a mixture obtained by dissolving, in diglyme, acopolymer represented by Chemical Formula 3 (i.e., a polymer including agroup which generates an acid when the polymer is heated) and a compoundrepresented by Chemical Formula 4 (i.e., a compound which generates abase when the compound is irradiated with an energy beam (ArF excimerlaser beam)) is used.

First, as shown in FIG. 1(a), the resist material is spin-coated onto asemiconductor substrate 100 made of silicon and the coated semiconductorsubstrate is pre-baked at a temperature of about 90° C. for about 90seconds, thereby forming a resist film 101 having a thickness of about 1μm. At this point, no peeling is observed and the resist film 101 showssatisfactory adhesion. In addition, as represented by Chemical Formula5, sulfonic acid is generated from the copolymer represented by ChemicalFormula 3 because of the heat generated by the pre-baking.

Next, by using a mask 103, the resist film 101 is irradiated with ArFexcimer laser beam 104 as energy beam, thereby transferring the patternof the mask 103 onto the resist film 101. Then,O-phenylacetyl-acetophenone-oxime is decomposed to generate benzylamineon the surface of an exposed area 101 a of the resist film 101 asrepresented by the chemical reaction in Chemical Formula 6.

An unexposed area 101 b of the resist film 101 shows strong acidicproperties owing to the function of a sulfonic acid group shown inChemical Formula 5. On the other hand, in the exposed area 101 a of theresist film 101, O-phenylacetyl-acetophenone-oxime is decomposed togenerate benzylamine having basic properties as represented by thechemical reaction in Chemical Formula 6. Since benzylamine cancels theacidic properties resulting from the function of the sulfonic acidgroup, a neutralization proceeds to a certain degree.

Since the unexposed area 101 b of the resist film 101 shows the strongacidic properties, water is more easily adsorbed into the unexposed area101 b as compared with the exposed area 101 a which has beenneutralized. In other words, since a group having strong acidicproperties exists in the unexposed area 101 b, hydrogen bonding withwater is strengthened in the unexposed area 101 b and thus water is morelikely to be absorbed thereto. In contrast, in the exposed area 101 a,hydrogen bonding with water is weakened by the neutralization and thuswater is less likely to be absorbed thereto.

Next, as shown in FIG. 1(b), the semiconductor substrate 100 is retainedin the air having a relative humidity of about 95% at a temperature ofabout 30° C. for about 30 minutes, thereby supplying water vapor 105onto the surface of the resist film 101. Then, water vapor 105 isadsorbed into the surface of the unexposed area 101 b, into which wateris more likely to be adsorbed, so that the adsorbed water diffuses intoa deep level, for example, at a depth of about 100 nm from the surfaceof the unexposed area 101 b. Since the exposed area 101 a has beenneutralized, water is less likely to be adsorbed thereto. As a result, awater-adsorbing layer 106 is selectively formed in the unexposed area101 b.

Then, as shown in FIG. 1(c), while retaining the semiconductor substrate100 in the air having a relative humidity of about 95% at a temperatureof about 30° C., vapor 107 of methyltriethoxysilane (MTEOS) is sprayedas a metal alkoxide onto the surface of the resist film 101 for about 30minutes. As a result, a metal oxide film 108 is selectively formed onthe surface of the unexposed area 101 b of the resist film 101. In thiscase, an acid (H³⁰ ) derived from sulfonic acid works as a catalyst toproduce the hydrolysis and the dehydration of MTEOS, thereby forming themetal oxide film 108. Therefore, the metal oxide film 108 grows only inthe area where both the acid (H⁺) serving as the catalyst and waterexist.

In the first embodiment, no metal oxide film is formed in the exposedarea 101 a of the resist film 101 because sulfonic acid is neutralizedby the generated benzylamine and loses its function as a catalyst andbecause water is less likely to be absorbed thereto. In contrast, themetal oxide film 108 is formed in the unexposed area 101 b of the resistfilm 101 because H⁺ serving as the catalyst exists there and asufficient amount of water has been absorbed thereto.

Next, as shown in FIG. 1(d), by using the metal oxide film 108 as amask, an RIE (reactive ion etching) process is performed by using O₂plasma 109, thereby forming a resist pattern 110. In this case, the RIEprocess using O₂ plasma is performed by using a parallel plate RIEsystem under the conditions where a power of about 900 W is supplied, apressure of about 0.7 Pa is applied and a flow rate is set at about 40SCCM.

In the first embodiment, since the metal oxide film 108 is selectivelyformed only in the unexposed area 101 b and the etching process isperformed by using the metal oxide film 108 as a mask, a positive typeresist pattern 110 having a vertical cross-sectional shape and a widthof about 0.15 μm can be formed in the unexposed area 101 b.

Furthermore, since water vapor 105 is supplied to the resist film 101 inthe process step shown in FIG. 1(b), water diffuses from the surface ofthe unexposed area 110 b of the resist film 101 into a deep level. Thus,the metal oxide film 108 grows so as to extend toward the inside of theresist film 101. As a result, a metal oxide film 108 having a largethickness can be formed.

In addition, since MTEOS is supplied to the resist film 101 in the airhaving a relative humidity of about 95% in the process step shown inFIG. 1(c), the equilibrium of water can be maintained. This is becauseit is possible to prevent the water, which has been absorbed into theresist film 101, from evaporating therefrom and because a sufficientamount of water required for forming the metal oxide film 108 can besupplied thereto. As a result, a metal oxide film 108 thick enough towithstand the RIE process using O₂ plasma can be formed.

As described above, in this first embodiment, the resist film 101, inwhich an acid has been generated from the copolymer through a heattreatment, is exposed to light. In the exposed area 101 a, a base isgenerated to neutralize the acidic properties of the exposed area 101 a,while the metal oxide film 108 is selectively formed only in theunexposed area 101 b. Thereafter, by using the metal oxide film 108 as amask, the resist film 101 is etched. Thus, it is possible to form apositive type fine resist pattern 110 having a desired shape.

Also, since water is forcedly absorbed into the unexposed area 101 bbefore the metal oxide film 108 is grown, it is possible to form a metaloxide film 108 having a sufficiently large thickness required for thedry development by the RIE process using O₂ plasma.

Furthermore, MTEOS is used as a metal alkoxide in this embodiment.Alternatively, any other metal alkoxide such as CH₃Si(OCH₃)₃(methyltrimethoxysilane), Si(OCH₃)₄ (tetramethoxysilane), Si(OC₂H₅)₄(tetraethoxysilane), Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃ or Zr(OC₂H₅)₃may be supplied in a vapor phase or in a liquid phase.

Also, the dry development is performed by the RIE process using O₂plasma in this embodiment. As an alternative, an ECR (electron cyclotronresonance) etching process using O₂ plasma may be performed. Moreover, amixture gas in which SO₂ gas or the like is added to O₂ gas may be usedas an alternative etching gas.

Furthermore, the exposing radiation is assumed to be an ArF excimerlaser beam in this embodiment. Alternatively, an i-beam, a KrF excimerlaser beam, VUV, EUV, EB, an X-ray or the like may also be used.

Furthermore, in the process step of diffusing water in the surfaceregion of the unexposed area 101 b of the resist film 101, thesemiconductor substrate 100 is retained within water vapor in thisembodiment. Alternatively, water in a liquid phase may be supplied tothe resist film 101 on the semiconductor substrate 100. However, watercan be more rapidly diffused and the depth of the metal oxide film 108can be increased when water is supplied in a vapor phase than in aliquid phase. Thus, water is preferably supplied in a vapor phase.

Embodiment 2

FIGS. 2(a) through 2(d) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the second embodiment ofthe present invention.

A mixture obtained by dissolving, in diglyme, a copolymer represented byChemical Formula 7 (i.e., a polymer including a group which generates anacid when the polymer is heated) and a compound represented by ChemicalFormula 8 (i.e., a compound which generates a base when the compound isirradiated with an energy beam (an ArF excimer laser beam)) is used as aresist material.

First, as shown in FIG. 2(a), the resist material is spin-coated onto asemiconductor substrate 200 made of silicon and the coated semiconductorsubstrate is pre-baked at a temperature of about 120° C. for about 90seconds, thereby forming a resist film 201 having a thickness of about 1μm. At this point, no peeling is observed and the resist film 201 showssatisfactory adhesion. In addition, as represented by Chemical Formula9, sulfonic acid is generated from the copolymer represented by ChemicalFormula 7 because of the heat generated by the pre-baking.

Next, by using a mask 203, the resist film 201 is irradiated with an ArFexcimer laser beam 204 as an energy beam, thereby transferring thepattern of the mask 203 onto the resist film 201. Then,O-phenylacetyl-acetophenone-oxime is decomposed to generate benzylamineon the surface of an exposed area 201 a of the resist film 201, asrepresented by the chemical reaction in Chemical Formula 10.

An unexposed area 201 b of the resist film 201 shows strong acidicproperties owing to the function of a sulfonic acid group shown inChemical Formula 9. On the other hand, in the exposed area 201 a of theresist film 201, O-phenylacetyl-acetophenone-oxime is decomposed togenerate benzylamine having basic properties as represented by thechemical reaction in Chemical Formula 10. Since benzylamine cancels theacidic properties resulting from the function of the sulfonic acidgroup, a neutralization proceeds to a certain degree.

Since the unexposed area 201 b of the resist film 201 shows the strongacidic properties, water is more easily adsorbed into the unexposed area201 b as compared with the exposed area 201 a which has beenneutralized. In other words, since a group having strong acidicproperties exists in the unexposed area 201 b, hydrogen bonding withwater is strengthened in the unexposed area 201 b and thus water is morelikely to be absorbed thereto. In contrast, in the exposed area 201 a,hydrogen bonding with water is weakened by the neutralization and thuswater is less likely to be absorbed thereto.

Next, as shown in FIG. 2(b), the semiconductor substrate 200 is retainedin the air having a relative humidity of about 95% at a temperature ofabout 30° C. for about 30 minutes, thereby supplying water vapor 205onto the surface of the resist film 201. Then, water vapor 205 isadsorbed into the surface of the unexposed area 201 b, into which wateris more likely to be adsorbed, and the adsorbed water diffuses into adeep level, for example, at a depth of about 100 nm from the surface ofthe unexposed area 201 b. Since the exposed area 201 a has beenneutralized, water is less likely to be adsorbed thereto. As a result, awater-adsorbing layer 206 is selectively formed in the unexposed area201 b.

Then, as shown in FIG. 2(c), while retaining the semiconductor substrate200 in the air having a relative humidity of about 95% at a temperatureof about 30° C., vapor 207 of methyltrimethoxysilane (MTMOS) is sprayedas a metal alkoxide onto the surface of the resist film 201 for about 20minutes. As a result, a metal oxide film 208 is selectively formed onthe surface of the unexposed area 201 b of the resist film 201. In thiscase, the acid (H⁺) derived from sulfonic acid works as a catalyst toproduce the hydrolysis and the dehydration of MTMOS, thereby forming themetal oxide film 208. Therefore, the metal oxide film 208 grows only inthe area where both the acid (H⁺) serving as the catalyst and waterexist.

In the second embodiment, no metal oxide film is formed in the exposedarea 201 a of the resist film 201 because sulfonic acid is neutralizedby the generated benzylamine and loses its function as a catalyst andbecause water is less likely to be absorbed thereto. In contrast, themetal oxide film 208 is formed in the unexposed area 201 b of the resistfilm 201 because H⁺ serving as a catalyst exists there and a sufficientamount of water has been absorbed thereto.

Next, as shown in FIG. 2(d), by using the metal oxide film 208 as amask, an RIE (reactive ion etching) process is performed by using O₂plasma 209, thereby forming a resist pattern 210. In this case, the RIEprocess using O₂ plasma is performed by using a parallel plate RIEsystem under the conditions where a power of about 900 W is supplied, apressure of about 0.7 Pa is applied and a flow rate is set at about 40SCCM.

In the second embodiment, since the metal oxide film 208 is selectivelyformed only in the unexposed area 201 b and the etching is performed byusing the metal oxide film 208 as a mask, a positive type resist pattern210 having a vertical cross-sectional shape and a width of about 0.15 μmcan be formed in the unexposed area 201 b.

Furthermore, since water vapor 205 is supplied to the resist film 201 inthe process step shown in FIG. 2(b), water diffuses from the surface ofthe unexposed area 201 b of the resist film 201 into a deep level. Thus,the metal oxide film 208 grows so as to extend toward the inside of theresist film 201. As a result, a metal oxide film 208 having a largethickness can be formed.

In addition, since MTMOS is supplied to the resist film 201 in the airhaving a relative humidity of about 95% in the process step shown inFIG. 2(c), the equilibrium of water can be maintained. This is becauseit is possible to prevent the water, which has been absorbed into theresist film 201, from evaporating therefrom and because a sufficientamount of water required for forming the metal oxide film 208 can besupplied thereto. As a result, a metal oxide film 208 thick enough towithstand the RIE process using O₂ plasma can be formed.

As described above, in this second embodiment, the resist film 201, inwhich an acid has been generated from the copolymer through a heattreatment, is exposed to light. In the exposed area 201 a, a base isgenerated to neutralize the acidic properties of the exposed area 201 a,while the metal oxide film 208 is selectively formed only in theunexposed area 201 b. Thereafter, by using the metal oxide film 208 as amask, the resist film 201 is etched. Thus, it is possible to form apositive type fine resist pattern 210 having a desired shape.

Also, since water is forcedly absorbed into the unexposed area 201 bbefore the metal oxide film 208 is grown, it is possible to form a metaloxide film 208 having a sufficiently large thickness required for thedry development by the RIE process using O₂ plasma.

In this embodiment, MTMOS is used as a metal alkoxide. Alternatively,any other metal alkoxide such as CH₃Si(OC₂H₅)₃(methyltriethoxysilane),Si(OCH₃)₄(tetramethoxysilane), Si(OC₂H₅)₄(tetraethoxysilane),Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃ or Zr(OC₂H₅)₃ may be supplied in avapor phase or in a liquid phase.

Also, the dry development is performed by the RIE process using O₂plasma in this embodiment. As an alternative, an ECR (electron cyclotronresonance) etching process using O₂ plasma may be performed. Moreover, amixture gas in which SO₂ gas or the like is added to O₂ gas may be usedas an alternative etching gas.

Furthermore, the exposing radiation is assumed to be an ArF excimerlaser beam in this embodiment. Alternatively, an i-beam, a KrF excimerlaser beam, VUV, EUV, EB, an X-ray or the like may also be used.

Furthermore, in the process step of diffusing water in the surfaceregion of the unexposed area 201 b of the resist film 201, thesemiconductor substrate 200 is retained within water vapor in thisembodiment. Alternatively, water in a liquid phase may be supplied tothe resist film 201 on the semiconductor substrate 200. However, watercan be more rapidly diffused and the depth of the metal oxide film 208can be increased when water is supplied in a vapor phase than in aliquid phase. Thus, water is preferably supplied in a vapor phase.

Embodiment 3

FIGS. 2(a) through 2(d) are cross-sectional views showing the respectiveprocess steps of a pattern forming method in the third embodiment of thepresent invention.

A mixture obtained by dissolving, in monoglyme, a copolymer representedby Chemical Formula 11 (i.e., a polymer including a group whichgenerates an acid when the polymer is heated) and a compound representedby Chemical Formula 12 (i.e., a compound which generates a base when thecompound is irradiated with an energy beam (an ArF excimer laser beam))is used as a resist material.

First, as shown in FIG. 2(a), the resist material is spin-coated onto asemiconductor substrate 200 made of silicon and the coated semiconductorsubstrate is pre-baked at a temperature of about 80° C. for about 90seconds, thereby forming a resist film 201 having a thickness of about 1μm. At this point, no peeling is observed and the resist film 201 showssatisfactory adhesion During this pre-baking process, no acid isgenerated from the copolymer represented by Chemical Formula 11.

Next, by using a mask 203, the resist film 201 is irradiated with an ArFexcimer laser beam 204 as an energy beam, thereby transferring thepattern of the mask 203 onto the resist film 201. Then,O-phenylacetyl-acetonaphtoneoxime is decomposed to generate benzylamineon the surface of an exposed area 201 a of the resist film 201.

Next, a pre-baking process is performed on the resist film 201 for about90 seconds at a temperature of about 120° C. As represented by thechemical reaction in Chemical Formula 13, sulfonic acid is generatedfrom the copolymer represented by Chemical Formula 11 because of theheat generated by the pre-baking process.

An unexposed area 201 b of the resist film 201 shows strong acidicproperties owing to the function of a sulfonic acid group shown inChemical Formula 13. On the other hand in the exposed area 201 a of theresist film 201, O-phenylacetyl-acetonaphtone-oxime is decomposed togenerate benzylamine having basic properties. Since benzylamine cancelsthe acidic properties resulting from the function of the sulfonic acidgroup, a neutralization proceeds to a certain degree.

Since the unexposed area 201 b of the resist film 201 shows the strongacidic properties, water is more easily adsorbed into the unexposed area201 b as compared with the exposed area 201 a which has beenneutralized. In other words, since a group having strong acidicproperties exists in the unexposed area 201 b, hydrogen bonding withwater is strengthened in the unexposed area 201 b and thus water is morelikely to be absorbed thereto. In contrast, in the exposed area 201 a,hydrogen bonding with water is weakened by the neutralization and thuswater is less likely to be absorbed thereto.

Next, as shown in FIG. 2(b), the semiconductor substrate 200 is retainedin the air having a relative humidity of about 95% at a temperature ofabout 30° C. for about 30 minutes, thereby supplying water vapor 205onto the surface of the resist film 201. Then, water vapor 205 isadsorbed into the surface of the unexposed area 201 b, into which wateris more likely to be adsorbed, and the adsorbed water diffuses into adeep level, for example, at a depth of about 100 nm from the surface ofthe unexposed area 201 b. Since the exposed area 201 a has beenneutralized, water is less likely to be adsorbed thereto. As a result, awater-adsorbing layer 206 is selectively formed in the unexposed area201 b.

Then, as shown In FIG. 2(c), while retaining the semiconductor substrate200 in the air having a relative humidity of about 95% at a temperatureof about 30° C., vapor 207 of methyltrimethoxysilane (MTMOS) Is sprayedas a metal alkoxide onto the surface of the resist film 201 for about 20minutes. As a result, a metal oxide film 208 is selectively formed onthe surface of the unexposed area 201 b of the resist film 201. In thiscase, the acid (H⁺) derived from sulfonic acid works as a catalyst toproduce the hydrolysis and the dehydration of MTMOS, thereby forming themetal oxide film 208. Therefore, the metal oxide film 208 grows only inthe area where both the acid (H⁺) serving as the catalyst and waterexist.

In the third embodiment, no metal oxide film is formed in the exposedarea 201 a of the resist film 201 because sulfonic acid is neutralizedby the generated benzylamine and loses its function as a catalyst andbecause water is less likely to be absorbed thereto. In contrast, themetal oxide film 208 is formed in the unexposed area 201 b of the resistfilm 201 because H⁺ serving as a catalyst exists there and a sufficientamount of water has been absorbed thereto.

Next, as shown in FIG. 2(d), by using the metal oxide film 208 as amask, an RIE (reactive ion etching) process is performed by using O₂plasma 209, thereby forming a resist pattern 210. In this case, the RIEprocess using O₂ plasma is performed by using a parallel plate RIEsystem under the conditions where a power of about 900 W is supplied, apressure of about 0.7 Pa is applied and a flow rate is set at about 40SCCM.

In the third embodiment, since the metal oxide film 208 is selectivelyformed only in the unexposed area 201 b and etching is performed byusing the metal oxide film 208 as a mask, a positive type resist pattern210 having a vertical cross-sectional shape and a width of about 0.15 μmcan be formed in the unexposed area 201 b.

Furthermore, since water vapor 205 is supplied to the resist film 201 inthe process step shown in FIG. 2(b), water diffuses from the surface ofthe unexposed area 201 b of the resist film 201 into a deep level. Thus,the metal oxide film 208 grows so as to extend toward the inside of theresist film 201. As a result, a metal oxide film 208 having a largethickness can be formed.

In addition, since MTMOS is supplied to the resist film 201 in the airhaving a relative humidity of about 95% in the process step shown inFIG. 2(c), the equilibrium of water can be maintained. This is becauseit is possible to prevent the water, which has been absorbed into theresist film 201, from evaporating therefrom and because a sufficientamount of water required for forming the metal oxide film 208 can besupplied thereto. As a result, a metal oxide film 208 thick enough towithstand the RIE process using O₂ plasma can be formed.

As described above, in this third embodiment, the resist film 201 isexposed to light, thereby generating a base in the exposed area 201 a.Thereafter, an acid is generated from the copolymer by heating the film,thereby neutralizing the basic properties of the exposed area 201 a,while the metal oxide film 208 is selectively formed only in theunexposed area 201 b. Then, by using the metal oxide film 208 as a mask,the resist film 201 is etched. Thus, it is possible to form a positivetype fine resist pattern 210 having a desired shape.

Also, since water is forcedly absorbed into the unexposed area 201 bbefore the metal oxide film 208 is grown, it is possible to form a metaloxide film 208 having a sufficiently large thickness required for thedry development by the RIE process using O₂ plasma.

In this embodiment, MTMOS is used as a metal alkoxide. Alternatively,any other metal alkoxide such as CH₃Si(OC₂H₅)₃ (methyltriethoxysilane),Si(OCH₃)₄ (tetramethoxysilane), Si(OC₂H₅)₄ (tetraethoxysilane),Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃ or Zr(OC₂H₅)₃ may be supplied in avapor phase or in a liquid phase.

Also, the dry development is performed by the RIE process using O₂plasma in this embodiment. As an alternative, an ECR (electron cyclotronresonance) etching process using O₂ plasma may be performed. Moreover, amixture gas in which SO₂ gas or the like is added to O₂ gas may be usedas an alternative etching gas.

Furthermore, the exposing radiation is assumed to be an ArF excimerlaser beam in this embodiment. Alternatively, an i-beam, a KrF excimerlaser beam, VUV, EUV, EB, an X-ray or the like may also be used.

Furthermore, in the process step of diffusing water in the surfaceregion of the unexposed area 201 b of the resist film 201, thesemiconductor substrate 200 is retained within water vapor in thisembodiment. Alternatively, water in a liquid phase may be supplied tothe resist film 201 on the semiconductor substrate 200. However, watercan be more rapidly diffused and the depth of the metal oxide film 208can be increased when water is supplied in a vapor phase than in aliquid phase. Thus, water is preferably supplied in a vapor phase.

Embodiment 4

FIGS. 3(a) through 3(c) and FIGS. 4(a) and 4(b) are cross-sectionalviews showing the respective process steps of a pattern forming methodin the fourth embodiment of the present invention.

A mixture obtained by dissolving, in diglyme, a copolymer represented byChemical Formula 14 (i.e., a polymer including a group which generatesan acid when the polymer is irradiated with the second energy beam (ani-beam)) and a compound represented by Chemical Formula 15 (i.e., acompound which generates a base when the compound is irradiated with thefirst energy beam (an ArF excimer laser beam)) is used as a resistmaterial.

First, as shown in FIG. 3(a), the resist material is spin-coated onto asemiconductor substrate 300 made of silicon, and the coatedsemiconductor substrate is heated at a temperature of about 90° C. forabout 90 seconds, thereby forming a resist film 301 having a thicknessof about 1 μm. At this point, no peeling is observed, and the resistfilm 301 shows satisfactory adhesion.

Next, by using a mask 303, the resist film 301 is irradiated with an ArFexcimer laser beam 304 as the first energy beam, thereby transferringthe pattern of the mask 303 onto the resist film 301. Then, O-tertiarybutylacetylacetophenone-oxime is decomposed to generate amine on thesurface of an exposed area 301 a of the resist film 301, as representedby the chemical reaction in Chemical Formula 16.

Next, as shown in FIG. 3(b), the entire surface of the resist film 301is exposed to an i-beam 305 as the second energy beam. Then, in theexposed area 301 a, which has been exposed to the ArF excimer laser beam304, sulfonic acid having acidic properties is generated in accordancewith the exposure of the entire surface of the resist film 301 to thei-beam 305, as represented by the chemical reaction in Chemical Formula9. As a result, the exposed area 301 a is neutralized.

On the other hand, the unexposed area 301 b of the resist film 301,which has not been exposed to the ArF excimer laser beam 304, showsacidic properties, because sulfonic acid is generated therein inaccordance with the exposure of the entire surface of the resist film301 to the i-beam 305, as represented by the chemical reaction inChemical Formula 17. In this case, since the unexposed area 301 b showsstrong acidic properties, water is more likely to be adsorbed thereto,as compared with the exposed area 301 a which has been neutralized.

Next, as shown in FIG. 3(a), the semiconductor substrate 300 is retainedwithin the air having a relative humidity of about 95% at a temperatureof about 30° C. for about 30 minutes, thereby supplying water vapor 307onto the surface of the resist film 301. Then, water vapor 307 isadsorbed into the surface of the unexposed area 301 b, into which wateris more likely to be adsorbed, and the adsorbed water diffuses into adeep level, for example, at a depth of about 100 nm from the surface ofthe unexposed area 301 b. Since the exposed area 301 a has beenneutralized, water is less likely to be adsorbed thereto. As a result, awater-adsorbing layer 308 is selectively formed in the unexposed area301 b.

Then, as shown in FIG. 4(a), while retaining the semiconductor substrate300 within the air having a relative humidity of about 95% at atemperature of about 30° C., vapor 309 of methyltriethoxysilane (MTEOS)is sprayed as a metal alkoxide onto the surface of the resist film 301for about 30 minutes. As a result, a metal oxide film 310 is selectivelyformed on the surface of the unexposed area 301 b of the resist film301. In this case, an acid (H⁺) derived from sulfonic acid works as acatalyst to produce the hydrolysis and the dehydration of MTEOS, therebyforming the metal oxide film 310. Therefore, the metal oxide film 310 isformed only in the area where both the acid (H⁺) serving as the catalystand water exist.

In the fourth embodiment, no metal oxide film is formed in the exposedarea 301 a of the resist film 301 because amine is neutralized by thegenerated sulfonic acid and loses its function as a catalyst and becausewater is less likely to be absorbed thereto. In contrast, the metaloxide film 310 is formed in the unexposed area 301 b of the resist film301 because the acid serving as the catalyst exists there and asufficient amount of water has been absorbed thereto.

Next, as shown in FIG. 4(b), by using the metal oxide film 310 as amask, an RIE (reactive ion etching) process is performed by using O₂plasma 311, thereby forming a resist pattern 312. In this case, the RIEprocess using O₂ plasma is performed by using a parallel plate RIEsystem under the conditions where a power of about 900 W is supplied, apressure of about 0.7 Pa is applied and a flow rate is set at about 40SCCM.

In the fourth embodiment, since the metal oxide film 310 is selectivelyformed only in the unexposed area 301 b and the etching is performed byusing the metal oxide film 310 as a mask, a positive type resist pattern312 having a vertical cross-sectional shape and a width of about 0.15 μmcan be formed in the unexposed area 301 b.

Furthermore, since water vapor 307 is supplied to the resist film 301 inthe process step shown in FIG. 3(c), water diffuses from the surface ofthe unexposed area 301 b of the resist film 301 into a deep level. Thus,the metal oxide film 310, grows so as to extend toward the inside of theresist film 301. As a result, a metal oxide film 310 having a largethickness can be formed. In particular, since the acid is generated onlyin the surface region of the resist film 301, the thickness of the wateradsorbing layer 308 can be limited so as not to exceed the depth of theregion where the acid has been generated. Thus, it is possible toprevent water from making a detour to reach the regions under theexposed area 301 a.

In addition, since MTEOS is supplied to the resist film 301 in the airhaving a relative humidity of about 95% in the process step shown inFIG. 4(a), the equilibrium of water can be maintained. This is becauseit is possible to prevent the water, which has been absorbed into theresist film 301, from evaporating therefrom and because a sufficientamount of water required for forming the metal oxide film 310 can besupplied thereto. As a result, a metal oxide film 310 thick enough towithstand the RIE process using O₂ plasma can be formed.

As described above, in this fourth embodiment, first, the resist film301 is exposed to the first energy beam, thereby generating a base inthe exposed area 301 a. Thereafter, the entire surface of the resistfilm 301 is exposed to the second energy beam, thereby generating anacid and neutralizing the exposed area 301 a which has been subjected toan exposure. On the other hand, the unexposed area 301 b is acidified,thereby selectively forming the metal oxide film 310 only in theunexposed area 301 b. And then the resist film 301 is etched by usingthe metal oxide film 310 as a mask. Thus, it is possible to form apositive type fine resist pattern 312 having a desired shape.

Also, since water is forcedly absorbed into the unexposed area 301 bbefore the metal oxide film 310 is grown, it is possible to form a metaloxide film 310 having a sufficiently large thickness required for thedry development by the RIE process using O₂ plasma.

In this embodiment, MTEOS is used as a metal alkoxide. Alternatively,any other metal alkoxide such as CH₃Si(OCH₃)₃ (methyltrimethoxysilane),Si(OCH₃)₄ (tetramethoxysilane), Si(OC₂H₅)₄ (tetraethoxysilane),Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃ or Zr(OC₂H₅)₃ may be supplied in avapor phase or in a liquid phase.

Also, the dry development is performed by the RIE process using O₂plasma in this embodiment. As an alternative, an ECR (electron cyclotronresonance) etching process using O₂ plasma may be performed. Moreover, amixture gas in which SO₂ gas or the like is added to O₂ gas may be usedas an alternative etching gas.

Furthermore, the exposing radiation is assumed to be an ArF excimerlaser beam in this embodiment. Alternatively, an i-beam, a KrF excimerlaser beam, VUV, EUV, EB, an X-ray or the like may also be used.

Furthermore, in the process step of diffusing water in the surfaceregion of the unexposed area 301 b of the resist film 301, thesemiconductor substrate 300 is retained within water vapor in thisembodiment. Alternatively, water in a liquid phase may be supplied tothe resist film 301 on the semiconductor substrate 300. However, watercan be more rapidly diffused and the depth of the metal oxide film 310can be increased when water is supplied in a vapor phase than in aliquid phase. Thus, water is preferably supplied in a vapor phase.

Variant of Embodiment 4

In this variant, a mixture of a polymer (e.g., a copolymer representedby Chemical Formula 14) including a group which generates an acid whenthe polymer is irradiated with the first energy beam (e.g., i-beam) anda compound (e.g., a compound represented by Chemical Formula 15) whichgenerates a base when the compound is irradiated with the second energybeam (e.g., ArF excimer laser beam) is used as a resist material.

First, the entire surface of a resist film is exposed to the firstenergy beam, thereby generating an acid from the copolymer. Then, theresist film is exposed to the second energy beam, thereby generating abase in the area of the resist film which has been exposed to the secondenergy beam. In such a case, in the area of the resist film which hasbeen exposed to the second energy beam, the acid which has beengenerated from the copolymer is neutralized with the base which has beengenerated from the compound.

On the other hand, in the area of the resist film, which has not beenexposed to the second energy beam, the acid, which has been generatedfrom the copolymer, is left. Thus, if water vapor and alkoxy silane aresupplied to the unexposed area after water is absorbed by supplyingwater vapor thereto, then a metal oxide film is formed therein.

Next, by etching the resist film by using the metal oxide film as amask, a resist pattern is formed.

In this variant of Embodiment 4, a positive type fine resist patternhaving a desired shape can also be formed in the same way as in thefirst to the fourth embodiments.

In the first to the fourth embodiments and in this variant of Embodiment4, a copolymer represented by Chemical Formula 3, a copolymerrepresented by Chemical Formula 7, a copolymer represented by ChemicalFormula 11 and a copolymer represented by Chemical Formula 14 are usedas the respective polymers. Alternatively, any other copolymer, such asthose represented by Chemical Formulae 18 to 24, including a group whichgenerates sulfonic acid may also be used. Moreover, a polymer includinga group having strong acidic properties may also be used instead of thepolymer including a group which generates sulfonic acid.

It is noted that the ratio of the group which generates sulfonic acid orthe group having strong acidic properties to the copolymer may be set atan arbitrary value. However, in order to facilitate the neutralizationwith the base, the ratio is preferably equal to or lower than about 50mol %.

In addition, in the first to the fourth embodiments and in this variantof Embodiment 4, any compound, such as those represented by ChemicalFormulae 25 to 30, including a group which generates amine may be usedas the compound which generates a base. Moreover, a compound whichgenerates a group having basic properties may also be used instead ofthe compound including a group which generates amine.

Moreover, in the first to the fourth embodiments and in this variant ofEmbodiment 4, a polymer including a group which generates sulfonic acidis used. Alternatively, a binary polymer obtained by polymerizing agroup, such as that represented by Chemical Formula 31, with thesulfonic acid generating group may be used instead.

Furthermore, in the fourth embodiment, the exposing radiation for theexposure with the first energy beam is assumed to be an ArF excimerlaser beam. Alternatively, an i-beam, a KrF excimer laser beam, EB, anX-ray or the like may also be used. In such a case, it is necessary touse a compound which generates a base upon the irradiation of theseenergy beam in place of the compound represented by Chemical Formula 15.Also, the exposing radiation for exposing the entire surface to thesecond energy beam is assumed to be an i-beam. Alternatively, any otherbeam may also be used. In such a case, it is necessary to use a polymerincluding a group which generates an acid upon the irradiation of otherenergy beam instead of the polymer represented by Chemical Formula 14.

In the first to the fourth embodiments, since the selectivity of themetal oxide film functioning as a surface modification film is notsatisfactory, some residue of the metal oxide film is adversely formedon the semiconductor substrate on which the resist pattern has beenformed.

Thus, it has been analyzed how benzylamine is generated by thedecomposition of O-phenylacetyl-acetophenone-oxime when the surface ofthe resist film is exposed to energy beam in the first embodiment. Themechanism how benzylamine is generated by the decomposition ofO-phenylacetyl-acetophenone-oxime is as represented by Chemical Formula32.

First, when light is irradiated onto O-phenylacetyl-acetophenone-oxime,the first reaction, i.e., a radical decomposition, is generated therein,so that O-phenylacetyl-acetophenone-oxime is decomposed into Radical a,CO₂ and Radical b. Thereafter, when the second reaction is generated,Radicals a and b are recombined. And then the third reaction, i.e., ahydrolysis with water in the air, occurs, thereby producing benzylamine.

In order to reduce the amount of the residue by increasing the amount ofthe base (OH⁻) generated in the unexposed area of the resist film, thepresent inventors repeatedly conducted experiments by increasing theamount of the ArF excimer laser beam as the exposing radiation. However,the residue could not be totally eliminated from the surface of thesemiconductor substrate.

On the other hand, when we caused the chemical reactions represented byChemical Formula 32 under various environments, we found that the amountof benzylamine to be produced differs depending upon the environmentwithin which the chemical reactions occur and also found that the secondreaction represented by Chemical Formula 32 is inhibited as a result ofthe influence of some impurity, such as carbon, existing in the air.That is to say, though the third reaction represented by ChemicalFormula 32, i.e., the hydrolysis with water in the air, is necessary,the second reaction is inhibited by the impurity such as carbon existingin the air during the hydrolysis.

Hereinafter, a method for reducing the amount of the residue of themetal oxide film remaining on the semiconductor substrate after theresist pattern has been formed thereon will be described.

Embodiment 5

Hereinafter, a pattern forming method in the fifth embodiment of thepresent invention will be described with reference to FIGS. 5(a) to 5(c)and FIGS. 6(a) to 6(c).

First, as shown in FIG. 5(a), a resist material having the followingcomposition is applied onto the surface of a semiconductor substrate400, thereby forming a resist film 401 having a thickness of about 0.5μm.

Polymer Poly (propylideneiminostyrene sulfonate (14  10 g mol%)-co-methyl methacrylate (86 mol %)) Base-generatingO-phenylacetyl-acetophenone-oxime 2.3 g Compound Solvent Diglyme  40 g

Next, the resist film 401 is heated (402) by a hot plate for about 60seconds at a temperature of about 90° C., thereby generating an acid(H⁺) over the entire surface region of the resist film 401 as shown inFIG. 5(b).

Next, as shown in FIG. 5(c), the resist film 401 is exposed to an ArFexcimer laser beam 404 (NA: about 0.55) at an energy of about 250 mJ/cm²by using a mask 403 having a desired pattern shape. It is noted that thereference numeral 401 a denotes an exposed area and 401 b denotes anunexposed area in FIG. 5(c).

Subsequently, as shown in FIG. 6(a), a water vapor treatment forsupplying water vapor 406 onto the entire surface of the resist film 401is performed within an environment of N₂ gas 405. In such a case, sincethe reaction is not inhibited by the impurity in the air, a sufficientamount of base (OH⁻) of benzylamine is produced fromO-phenylacetyl-acetophenone-oxime as the base-generating compound in theexposed area 401 a of the resist film 401, and the acid (H⁺) existing inthe resist film 401 is neutralized substantially completely with thesufficient amount of base (OH⁻) which has been produced.

Then, as shown in FIG. 6(b), a water vapor treatment for supplying watervapor 406 and a chemical vapor deposition (CVD) process for supplyingmethyltrimethoxysilane 407 are performed on the entire surface of theresist film 401. As a result, a polysiloxane film 408 is formed as ametal oxide film only in the unexposed area 401 b of the resist film401.

Next, as shown in FIG. 6(a), the resist film 401 is dry-etched by O₂ gas409 by using the polysiloxane film 408 as a mask, thereby developing thefilm and forming a resist pattern 410. In such a case, no residue isformed in the exposed area 401 a of the resist film 401.

In the fifth embodiment, since the water vapor treatment for supplyingwater vapor 406 onto the entire surface of the resist film 401 isperformed within an environment of N₂ gas 405, the second reactionrepresented by Chemical Formula 32 is not inhibited and the thirdreaction represented by Chemical Formula 32 is promoted. As a result, itis possible to improve the efficiency with which the base is generatedfrom the base-generating compound.

Embodiment 6

Hereinafter, a pattern forming method in the sixth embodiment of thepresent invention will be described with reference to FIGS. 5(a) to5(c), FIGS. 6(b) and 6(c) and FIGS. 7(a) and 7(b).

First, as shown in FIG. 5(a), a resist material having the samecomposition as that of the material used in the fifth embodiment isapplied onto the surface of a semiconductor substrate 400, therebyforming a resist film 401. Next, the resist film 401 is heated (402) bya hot plate for about 60 seconds at a temperature of about 90° C.,thereby generating an acid (H⁺) over the entire surface region of theresist film 401 as shown in FIG. 5(b). Thereafter, as shown in FIG.5(c), the resist film 401 is exposed to an ArF excimer laser beam 404through a mask 403 having a desired pattern shape.

Subsequently, as shown in FIG. 7(a), water 420 in a liquid phase or in avapor phase is supplied onto the entire surface of the resist film 401.In such a case, since O-phenylacetyl-acetophenone-oxime functioning asthe base-generating compound absorbs a large quantity of water, asufficient amount of base (OH⁻) of benzylamine is produced fromO-phenylacetyl-acetophenone-oxime in the exposed area 401 a of theresist film 401, and the acid (H⁺) existing in the resist film 401 isneutralized substantially completely with the sufficient amount of base(OH⁻) which has been produced.

Then, as shown in FIG. 7(b), a water vapor treatment for supplying watervapor 406 is performed on the entire surface of the resist film 401.Subsequently, as shown in FIG. 6(b), a water vapor treatment forsupplying water vapor 406 and a chemical vapor deposition (CVD) processfor supplying methyltrimethoxysilane 407 are performed on the entiresurface of the resist film 401. As a result, a polysiloxane film 408 isformed as a metal oxide film only in the unexposed area 401 b of theresist film 401.

Next, as shown in FIG. 6(a), the resist film 401 is dry-etched by O₂ gas409 by using the polysiloxane film 408 as a mask, thereby developing thefilm and forming a resist pattern 410. In such a case, no residue isformed in the exposed area 401 a of the resist film 401.

In the sixth embodiment, since water 420 in a vapor phase or in a liquidphase is supplied onto the resist film 401, the third reactionrepresented by Chemical Formula 32 is promoted. As a result, it ispossible to improve the efficiency with which the base is generated fromthe base-generating compound.

Embodiment 7

Hereinafter, a pattern forming method in the seventh embodiment of thepresent invention will be described with reference to FIGS. 5(a) to5(c), FIGS. 6(b) and 6(c) and FIGS. 8(a) and 8(b).

First, as shown in FIG. 5(a), a resist material having the samecomposition as that of the material used in the fifth embodiment isapplied onto the surface of a semiconductor substrate 400, therebyforming a resist film 401. Next, the resist film 401 is heated (402) bya hot plate for about 60 seconds at a temperature of about 90° C.,thereby generating an acid (H⁺) over the entire surface region of theresist film 401 as shown in FIG. 5(b). Thereafter, as shown in FIG.5(c), the resist film 401 is exposed to an ArF excimer laser beam 404 byusing a mask 403 having a desired pattern shape.

Subsequently, as shown in FIG. 8(a), the resist film 401 is retainedwithin an environment of N₂ gas 430. In such a case, since the reactionis not inhibited by the impurity in the air, a sufficient amount of base(OH⁻) of benzylamine is produced from O-phenylacetyl-acetophenone-oximefunctioning as the base-generating compound in the exposed area 401 a ofthe resist film 401, and the acid (H⁺) existing in the resist film 401is neutralized substantially completely with the sufficient amount ofbase (OH⁻) which has been produced.

Then, as shown in FIG. 8(b), a water vapor treatment for supplying watervapor 406 is performed on the entire surface of the resist film 401.Subsequently, as shown in FIG. 6(b), a water vapor treatment forsupplying water vapor 406 and a chemical vapor deposition (CVD) processfor supplying methyltrimethoxysilane 407 are performed on the entiresurface of the resist film 401. As a result, a polysiloxane film 408 isformed as a metal oxide film only in the unexposed area 401 b of theresist film 401.

Next, as shown in FIG. 6(c), the resist film 401 is dry-etched by O₂ gas409 by using the polysiloxane film 408 as a mask, thereby developing thefilm and forming a resist pattern 410. In such a case, no residue isformed in the exposed area 401 a of the resist film 401.

In the seventh embodiment, since the resist film 401 is retained withinan environment of N₂ gas 430, the second reaction represented byChemical Formula 32 is not inhibited. As a result, it is possible toimprove the efficiency with which the base is generated from thebase-generating compound.

In the fifth and the seventh embodiments, the N₂ gas 405, 430 is used asan inert gas. Alternatively, any other inert gas such as Ar gas may alsobe used.

Moreover, in the fifth to the seventh embodiments,methyltrimethoxysilane 407 is supplied as alkoxy silane. Alternatively,methyltriethoxysilane, ethyltriethoxysilane, ethyltrimethoxysilane orthe like may also be supplied. It is noted that the present invention isnot limited to any of these compounds.

Furthermore, in the fifth to the seventh embodiments, the dry etchingprocess is performed by using O₂ gas. Alternatively, a mixture gas inwhich SO₂ gas or the like is added to O₂ gas may also be used as anetching gas.

Furthermore, in the fifth to the seventh embodiments, the exposingradiation is assumed to be an ArF excimer laser beam. However, thepresent invention is not limited thereto, but VUV light such as F₂ lightand light having a wavelength of about 13 nm, an electron beam, an X-rayor the like may also be used.

What is claimed is:
 1. A pattern forming material comprising a polymerincluding a group which generates an acid when the polymer is heated anda compound which generates a base when the compound is irradiated withan energy beam.
 2. The pattern forming material of claim 1, wherein saidpolymer is a binary polymer or a polymer of a higher degree obtained bypolymerizing another group with a compound represented by the followinggeneral formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group.
 3. The pattern forming material ofclaim 1, wherein said polymer is a binary polymer or a polymer of ahigher degree obtained by polymerizing another group with a compoundrepresented by the following general formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₄ indicatesan alkyl group, an alkenyl group, a cyclic alkyl group or a cyclicalkenyl group.
 4. The pattern forming material of claim 1, wherein thecompound is acyloxime, a benzyloxycarbonyl compound or formamide.
 5. Apattern forming material comprising: a polymer including a group whichgenerates an acid when the polymer is irradiated with a first energybeam having a first energy band and a compound which generates a basewhen the compound is irradiated with a second energy band which isdifferent from the first energy band wherein said polymer is a binarypolymer or a polymer of a higher degree obtained by polymerizing anothergroup with a compound represented by the following general formula:

where R₁ indicates a hydrogen atom or an alkyl group, and R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group.